Faster, simpler, more efficient, and sustainable: A new method for detecting illicit drugs on surfaces

The research group FQM-215 - Affordable and Sustainable Sample Preparation at the University of Córdoba has developed a method that is not only faster and easier to perform but also more environmentally sustainable. It can detect illicit drugs on surfaces and determine their exact quantity in just five minutes, using everyday items such as cotton fabric swabs for sampling.

As explained by Carlos Calero Cañuelo, a member of the study alongside Rafael Lucena and Soledad Cárdenas, the process involves two main stages: sampling and analysis. In the first stage, the team has successfully combined a common household item with a reduction in toxic chemicals, minimizing the test’s environmental impact. A small cotton fabric swab, which is highly absorbent due to its cellulose composition, moistened with just a few drops of methanol, is sufficient to “capture” drug residues on surfaces.

Once the cotton fabric swab has absorbed the substances, the analysis begins. The method combines thermal desorption (evaporation) with mass spectrometry; an analytical technique used to identify molecules in a sample, both of which are essential for determining the type and quantity of the drug. After sampling, the swab is placed in a specialized interface for heating, causing the target compounds to evaporate. These compounds then enter a second phase where they are ionized using plasma, which gives them a positive charge. This allows the mass spectrometer, which employs electromagnetic fields, to accurately detect and measure the drugs.

“The use of mass spectrometry allows us to achieve very high levels of sensitivity and selectivity,” explains Calero Cañuelo. In fact, the method is so precise that it can detect drug residues invisible to the naked eye—down to 4 nanograms on a 100-square-centimeter surface.

Published in Analytica Chimica Acta, the method has been validated for a variety of drugs, including cocaine, methadone, and codeine, and tested across different surfaces and cotton swabs of various colors. Its combination of accuracy and simplicity makes it well suited for forensic applications, drug control, criminal investigations, and laboratory use.

Reference

Carlos Calero-Cañuelo, Rafael Lucena, Soledad Cárdenas, “Quantitative determination of drug residues in surfaces, analyzing cotton swabs by on/off thermal desorption-plasma based ionization-mass spectrometry,” Analytica Chimica Acta, Volume 1376, 2025, 344630, https://doi.org/10.1016/j.aca.2025.344630.